Electronic printers receive image data from computer work stations, word processors, and the like, which generally produce print jobs as character code signals for storage in a print server to be spooled one page at a time to a pattern generator for conversion to a rasterized video data stream. Electronic copiers receive image data from scanners, which convert the image on an original to a video data stream. The video data for printers and/or copiers may be stored in multi-page buffer memories. When a plurality of sets of a multi-page document are to be produced, the stored data for each page are repeatedly sent to the printer in proper page order such that the reproduction sets are automatically collated.
The number of pages which can be stored for a single job is limited by the size of the buffer memory and the memory space required per page. Accordingly, it is known to compress the data before storage, and to expand the data as it is withdrawn from storage. The compression ratio varies from original to original. Some pages, such as those containing continous tone images, may in fact, have a compression ratio less than one if subjected to many of the popular data compression algorithms. When these pages are present in a stored document, the number of pages which fit in buffer storage is greatly reduced.